Hi, Simon Riggs wrote:
Classification of Replication Techniques
Thanks for your classifications. It helps a great deal to clarify.
Type 2 is where you ship the WAL (efficient) then use it to reconstruct SQL (flexible) and then apply that to other nodes. It is somewhat harder than type 1, but requires less infrastructure (IMHO). Definitely requires less data shipping from Primary node, so very possibly more efficient.
What leads you to that conclusion? AFAICT a logical format, specifically designed for replication is quite certainly more compact than the WAL (assuming that's what you mean by "less data").
The only efficiency gain I can see compared to type 1 is, that most of the processing work is offloaded from the master to the slave(s). For setups with multiple slaves, that's a bad trade-off, IMO.
Previously, most RDBMS vendors supported type 1a) systems. They have now moved to type 2 and 3 systems. Both DB2 and Oracle support a type 2 *and* a type 3 replication system. The reasons they do this are valid for us also, so I suggest that we do the same. So for me, it is not about whether we do type 2 or type 3, I think we should do both.
I currently don't think type 2 is doable with any reasonable effort, but hey, I'm always open for surprises. :-)
Which of IBM's and Oracle's products are you referring to? Regards Markus Wanner -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
